Single phase regeneration with a polyphase rectification power circuit

Abstract

A polyphase rectifier power circuit with single phase regenerative capability provides motoring power from a polyphase supply and returns single phase regenerative power to the supply. One embodiment uses pulse width modulation of the regenerative rectifier to limit line-to-line current flow through the regenerative rectifier during regeneration while another embodiment uses 180° conduction in the regenerative rectifier with the substitution of two thyristors for two diodes in the rectifier.

What is claimed is: 
     
       1. A circuit for supplying rectified power to a load from a three phase ac source and providing single phase regeneration from the load to the three phase source, comprising: a three phase bridge rectifier including a plurality of rectifying elements, said rectifier adapted to be coupled to said three phase ac source;   controllable switch means with self-commutating ability coupled in inverse parallel with each of said rectifying elements respectively, in the first and second phases of said rectifier, said controllable switch means forming a single phase inverter;   first current sensing means for sensing current in the third phase of said rectifier;   second current sensing means for sensing the direction of current to the load; and   control means coupled to said switch means and said first and second current sensing means, said control means being responsive to direction and amplitude of current in the third phase of said rectifier for switching said switch means during regeneration, said control means including means for comparing relative voltages of said first and second phases of the ac source to determine conduction intervals of said switch means when providing regenerative current to the first and second phases of said source, and means coupled to said first current sensing means for pulse width modulating said controllable switch means to maintain said third phase rectifier current within predetermined positive and negative current limits.   
     
     
       2. The circuit in claim 1 wherein said three phase bridge rectifier comprises a full bridge rectifier. 
     
     
       3. The circuit in claim 2 wherein said controllable switch means comprises a bipolar transistor. 
     
     
       4. A circuit for supplying rectified power to a load from a three phase ac source and providing single phase regeneration from the load to the three phase source comprising: a three phase bridge rectifier including a plurality of rectifying elements in the first and second phases thereof and at least one controllable rectifying element in the third phase thereof, said rectifier adapted to be coupled to a three phase ac source;   controllable switch means with self-commutating ability coupled in inverse parallel with each of said rectifying elements, respectively, in the first and second phases of said rectifier, said controllable switch means forming a single phase inverter;   current sensing means for sensing direction of current to the load; and   control means coupled to said switch means, said current sensing means, and said controllable rectifying elements, said control means being responsive to direction of said current for switching on said switch means during regeneration and switching on said controllable rectifying elements during rectification, said control means including means for comparing relative voltages of said first and second phases of said ac source to determine conduction intervals of said switch means when providing regenerative current to the first and second phase of said source.   
     
     
       5. The claim of claim 4 wherein said three phase bridge rectifier comprises a full bridge rectifier. 
     
     
       6. The circuit in claim 5 wherein said controllable rectifying element comprises a thyristor and said controllable switch comprises a bipolar transistor. 
     
     
       7. The circuit in claim 5 wherein said control means further comprises: means coupled to said first and second phases of said rectifier for determining the conduction interval of said controllable rectifying elements in said third phase of said rectifier dependent on the relative voltages of said three phase ac source.